(1) We plan to conclude the medium-sized mammal susceptibility studies by testing the susceptibility of the woodchuck (Marmota monax) to infection by LAC virus via the bite of infected mosquitoes, and, in turn, if it can infect susceptible Ae. triseriatus. We plan to conclude the oral transmission experiments by feeding infected mosquitoes to chipmunks to determine if they can become infected, and serve as a source of infectious blood meals. (2) The LACV strain variation experiments are currently being continued to determine the infectivity that our geographically different strains have for Ae. triseriatus. Also, we have begun assay of these LAC virus strains for the occurrence of temperature sensitive (Ts) mutants, and to determine if mosquito-mosquito serial passage, without intervening vertebrate infection, selects for an increase in the Ts population. We will try to obtain additional LAC virus strains from the eastern part of its range (Ohio and eastern Indiana), to determine if strains from this area have the same lower neurovirulence and small, uniform plaque size that the 1977 Ohio strain has. (3) The reassortants and their LAC and SSH virus parents will be tested in snowshoe hares, assuming that we have more success at finding susceptible individuals in the field than we have had in the past 18 months.